Heavier group 2 metal complexes with a flexible scorpionate ligand based on 2-mercaptopyridine

摘要

We report the synthesis of novel alkaline earth metal complexes [ κ ~(2) -SS-(Bmp) _(2) M(THF) _( n ) ] [M = Ca ( 2 ), Sr ( 3 ) n = 2; M = Ba ( 4 ), n = 3] of a flexible dihydrobis(2-thiopyridone)borate ( Bmp ) ligand based on 2-mercaptopyridine. Complexes 2–4 were isolated in good yield by the reaction between sodium dihydrobis(2-thiopyridone)borate, [{(Bmp)Na(THF)} _(2) ] _( n ) ( 1 ) and the corresponding alkaline earth metal diiodides in toluene at ambient temperature. The solid-state structures of the strontium and barium complexes, complexes 3 and 4 respectively, were established using single-crystal X-ray diffraction analysis. The solid-state structure of sodium complex 1 was also confirmed using X-ray techniques. The solid-state structures of complexes 3 and 4 revealed that the Bmp ligand coordinates through sulphur atoms to the metal ions in κ ~(2) fashion. The strontium ion is attached symmetrically and the barium ion is asymmetrically linked with the Bmp ligand, manifesting the 2-thiopyridone and pyridine-2-thiolate tautomeric form of the Bmp ligand. The strontium ion in complex 3 adopts a distorted octahedral geometry whereas the geometry around the barium ion can best be described as a distorted pentagonal bipyramidal. Both complexes 3 and 4 also have a short B?H?M interaction due to the presence of the BH _(2) group in the ligand. In the solid state, sodium complex 1 is polymeric in nature and in the asymmetric unit each sodium ion is bonded to two sulphur atoms through η ~(1) and μ ~(2) modes. The adjacent BH _(2) group is also linked with each sodium ion through hydrogen atoms via μ ~(2) and η ~(1) .